sort list based on another list java

1. The Comparator.comparing static function accepts a sort key Function and returns a Comparator for the type that contains the sort key: To see this in action, we'll use the name field in Employee as the sort key, and pass its method reference as an argument of type Function. If we sort the Users, and two of them have the same age, they're now sorted by the order of insertion, not their natural order, based on their names. Not the answer you're looking for? Else, run a loop till the last node (i.e. If not then just replace SortedMap indexToObj by SortedMap> indexToObjList. Given parallel lists, how can I sort one while permuting (rearranging) the other in the same way? There are a few of these built-in comparators that work with numbers (int, double, and long) - comparingInt(), comparingDouble(), and comparingLong(). I don't know if it is only me, but doing : Please add some more context to your post. One with the specific order the lists should be in (listB) and the other has the list of items (listA). Why is this sentence from The Great Gatsby grammatical? If the elements of the stream are not Comparable, a java.lang.ClassCastException may be thrown upon execution. 2023 DigitalOcean, LLC. 12 is less than 21 and no one from L2 is in between. vegan) just to try it, does this inconvenience the caterers and staff? Do I need to loop through them and pass them to the compare method? How to sort one list and re-sort another list keeping same relation python? How can we prove that the supernatural or paranormal doesn't exist? Designed by Colorlib. Can airtags be tracked from an iMac desktop, with no iPhone? Just encountered the same problem. This is an old question but some of the answers I see posted don't actually work because zip is not scriptable. For bigger arrays / vectors, this solution with numpy is beneficial! All the elements in the list must implement Comparable interface, otherwise IllegalArgumentException is thrown. See JB Nizet's answer for an example of a custom Comparator that does this. "After the incident", I started to be more careful not to trip over things. You should instead use [x for (y,x) in sorted(zip(Y,X), key=lambda pair: pair[0])]. @Hatefiend interesting, could you point to a reference on how to achieve that? What sort of strategies would a medieval military use against a fantasy giant? The Collections (Java Doc) class (part of the Java Collection Framework) provides a list of static methods which we can use when working with collections such as list, set and the like. your map should be collected to a LinkedHashMap in order to preserve the order of listB. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Like Tim Herold wrote, if the object references should be the same, you can just copy listB to listA, either: Or this if you don't want to change the List that listA refers to: If the references are not the same but there is some equivalence relationship between objects in listA and listB, you could sort listA using a custom Comparator that finds the object in listB and uses its index in listB as the sort key. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Using a For-Each Loop One way of doing this is looping through listB and adding the items to a temporary list if listA contains them: Not completely clear what you want, but if this is the situation: I see where you are going with it, but you need to rethink what you were going for and edit this answer. The sort method orders the elements in their natural order which is ascending order for the type Integer.. You posted your solution two times. Once you have that, define your own comparison function which compares values based on the indexes of list Y. Once, we have sorted the list, we build the HashMap based on this sorted list. In this tutorial, we'll compare some filtering implementations and discuss their advantages and drawbacks. If the list is greater than or equal to 3 split list in two 0 to 2 and 3 to end of list. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Here is a solution that increases the time complexity by 2n, but accomplishes what you want. Since Comparator is a functional interface, we can use lambda expressions to write its implementation in a single line. The most obvious solution to me is to use the key keyword arg. Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Create a Map that maps the values of everything in listB to something that can be sorted easily, such as the index, i.e. Here if the data type of Value is String, then we sort the list using a comparator. Key and Value can be of different types (eg - String, Integer). Premium CPU-Optimized Droplets are now available. - the incident has nothing to do with me; can I use this this way? Merge two lists in Java and sort them using Object property and another condition, How Intuit democratizes AI development across teams through reusability. Do you know if there is a way to sort multiple lists at once by one sorted index list? Returning a negative number indicates that an element is lesser than another. It only takes a minute to sign up. From simple plot types to ridge plots, surface plots and spectrograms - understand your data and learn to draw conclusions from it. Sorry, that was my typo. How can I randomly select an item from a list? Once we have the list of values in a sorted manner, we build the HashMap again based on this new list. Oh, ignore, I can do sorted(zip(Index,X,Y,Z)) too. Find centralized, trusted content and collaborate around the technologies you use most. Speed improvement on JB Nizet's answer (from the suggestion he made himself). This is a very nice way to sort the list, and to clarify, calling with appendFirst=true will sort the list as [d, c, e, a, b], @boxed__l: It will sort the elements contained in both lists in the same order and add at the end the elements only contained in A. Thanks for learning with the DigitalOcean Community. I am also wandering if there is a better way to do that. . A:[c,b,a] More general case (sort list Y by any key instead of the default order), http://scienceoss.com/sort-one-list-by-another-list/, How Intuit democratizes AI development across teams through reusability. Not the answer you're looking for? Better example data would be quite helpful, too. No spam ever. I think that the title of the original question is not accurate. Why are physically impossible and logically impossible concepts considered separate in terms of probability? not if you call the sort after merging the list as suggested here. All times above are in ranch (not your local) time. If the list is less than 3 do nothing. Is it possible to create a concave light? In addition, the proposed solution won't work for the initial question as the lists X and Y contain different entries. Something like this? Assuming that the larger list contains all values in the smaller list, it can be done. Now it actually works. If you already have a dfwhy converting it to a list, process it, then convert to df again? The signature of the method is: It also returns a stream sorted according to the provided comparator. What I am doing require to sort collection of factories and loop through all factories and sort collection of their competitors. Is the God of a monotheism necessarily omnipotent? In java 6 or lower, you need to use. It returns a stream sorted according to the natural order. You can do list1.addAll(list2) and then sort list1 which now contains both lists. The answer of riza might be useful when plotting data, since zip(*sorted(zip(X, Y), key=lambda pair: pair[0])) returns both the sorted X and Y sorted with values of X. IMO, you need to persist something else. What is the shortest way of sorting X using values from Y to get the following output? Now it produces an iterable object. Learn more about Stack Overflow the company, and our products. You are using Python 3. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. That's easily managed with an index list: Since the decorate-sort-undecorate approach described by Whatang is a little simpler and works in all cases, it's probably better most of the time. B:[2,1,0], And you want to load them both and then produce: How to Sort a List by a property in the object. 2023 DigitalOcean, LLC. Thanks. That is, the first items (from Y) are compared; and if they are the same then the second items (from X) are compared, and so on. Using Java 8 Streams. For cases like these, we'll want to write a custom Comparator: And now, when we execute this code, we've got the natural order of names, as well as ages, sorted: Here, we've used a Lambda expression to create a new Comparator implicitly and defined the logic for sorting/comparison. How to use Slater Type Orbitals as a basis functions in matrix method correctly? rev2023.3.3.43278. This work is licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 4.0 International License. Make the head as the current node and create another node index for later use. My use case is this: user has a list of items initially (listA). With this method: Sorting a 1000 items list 100 times improves speed 10 times on my Replacing broken pins/legs on a DIP IC package. On the other hand, a Comparator is a class that is comparing 2 objects of the same type (it does not compare this with another object). Both of these variations are instance methods, which require an object of its class to be created before it can be used: This methods returns a stream consisting of the elements of the stream, sorted according to natural order - the ordering provided by the JVM. Let's say you have a listB list that defines the order in which you want to sort listA. The solution here is not to make your class implements Comparator and define a custom comparator class, like. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How can this new ban on drag possibly be considered constitutional? This method returns a lexicographic-order comparator with another comparator. How to make it come last.? Are there tables of wastage rates for different fruit and veg? Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? Overview. The code below is general purpose for a scenario where listA is a list of Objects since you did not indicate a particular type. Basically, this answer is nonsense. Note: Any item not in list1 will be ignored since the algorithm will not know what's the sort order to use. Stream.sorted() method : This Stream method is an stateful intermediate operation which sorts elements present in the stream according to natural order Unsubscribe at any time. If they are already numpy arrays, then it's simply. This is just an example, but it demonstrates an order that is defined by a list, and not the natural order of the datatype: Now, let's say that listA needs to be sorted according to this ordering. Specifically, we're using the comparingInt() method, and supplying the user's age, via the User::getAge method reference. (This is a very old answer!). You can use this generic comparator to sort list based on the the other list. Short story taking place on a toroidal planet or moon involving flying. Sorting list according to corresponding values from a parallel list [duplicate]. If changes are possible, you would need to somehow listen for changes to the original list and update the indices inside the custom list. How To Install Grails on an Ubuntu 12.04 VPS, Simple and reliable cloud website hosting, New! 2013-2023 Stack Abuse. my case was that I have list that user can sort by drag and drop, but some items might be filtered out, so we preserve hidden items position. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why do many companies reject expired SSL certificates as bugs in bug bounties? Linear regulator thermal information missing in datasheet, Short story taking place on a toroidal planet or moon involving flying, Identify those arcade games from a 1983 Brazilian music video, It is also probably wrong to have your class implements. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Why is "1000000000000000 in range(1000000000000001)" so fast in Python 3? For bigger arrays / vectors, this solution with numpy is beneficial! We can use Collections.reverseOrder () method, which returns a Comparator, for reverse sorting. Note: the key=operator.itemgetter(1) solves the duplicate issue, zip is not subscriptable you must actually use, If there is more than one matching it gets the first, This does not solve the OPs question. HashMaps are a good method for implementing Dictionaries and directories. All Rights Reserved. The String class implements Comparable interface. Thanks for contributing an answer to Code Review Stack Exchange! If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? 2023 ITCodar.com. If the age of the users is the same, the first one that was added to the list will be the first in the sorted order. Any suggestions? A example will show this. more_itertools has a tool for sorting iterables in parallel: I actually came here looking to sort a list by a list where the values matched. Is there a single-word adjective for "having exceptionally strong moral principles"? More elegant code or using some built in Java class? rev2023.3.3.43278. Zip the two lists together, sort it, then take the parts you want: Also, if you don't mind using numpy arrays (or in fact already are dealing with numpy arrays), here is another nice solution: I found it here: Sorting a 10000 items list 100 times improves speed 140 times (265 ms for the whole batch instead of 37 seconds) on my unit tests. Learn more about Stack Overflow the company, and our products. The size of both list must be same to use this trick. Then you can create your custom Comparator that uses the Map to create an order: Then you can sort listA using your custom Comparator. This can create unstable outputs unless you include the original list indices for the lexicographic ordering to keep duplicates in their original order. Check out our offerings for compute, storage, networking, and managed databases. In this quick tutorial, we'll learn how to find items from one list based on values from another list using Java 8 Streams. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? Is there a solution to add special characters from software and how to do it. L1-50 first, L2-50 next, then, L2-45, L2-42, L1-40 and L1-30. There are plenty of ways to achieve this. We can use the following methods to sort the list: Using stream.sorted () method Using Comparator.reverseOrder () method Using Comparator.naturalOrder () method Using Collections.reverseOrder () method Using Collections.sort () method Java Stream interface Java Stream interface provides two methods for sorting the list: sorted () method We can also create a custom comparator to sort the hash map according to values. Sorting a Java list collection using Lambda expression Since Java 8 with Lambda expressions support, we can write a comparator in a more concise way as follows: 1 Comparator<Book> descPriceComp = (Book b1, Book b2) -> (int) (b2.getPrice () - b1.getPrice ()); Using Kolmogorov complexity to measure difficulty of problems? then the question should be 'How to sort a dictionary? So you could simply have: What I am doing require to sort collection of factories and loop through all factories and sort collection of their competitors. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? We've used the respective comparison approaches for the names and ages - comparing names lexicographically using compareTo(), if the age values are the same, and comparing ages regularly via the > operator. I have a list of ordered keys, and I need to order the objects in a list according to the order of the keys. To avoid having a very inefficient look up, you should index the items in listB and then sort listA based on it. Making statements based on opinion; back them up with references or personal experience. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. That's right but the solutions use completely different methods which could be used for different applications. In Java How to Sort One List Based on Another. We first get the String values in a list. The preferred way to add something to SortedDependingList is by already knowing the index of an element and adding it by calling sortedList.addByIndex(index); If the two lists are guaranteed to contain the same elements, just in a different order, you can use List listA = new ArrayList<>(listB) and this will be O(n) time complexity. People will search this post looking to sort lists not dictionaries. ', not 'How to sorting list based on values from another list?'. To learn more, see our tips on writing great answers. May be just the indexes of the items that the user changed. unit tests. 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For example if. Output: Lets see another example where we will sort a list of custom objects. So we pass User::getCreatedOn to sort by the createdOn field. The best answers are voted up and rise to the top, Not the answer you're looking for? Warning: If you run it with empty lists it crashes. If so, how close was it? This tutorial covered sorting of HashMap according to Value. You return. I am also wandering if there is a better way to do that. Another solution that may work depending on your setting is not storing instances in listB but instead indices from listA. If the data is related then the data should be stored together in a simple class. We can sort a list in natural ordering where the list elements must implement Comparable interface. What do you mean when you say that you're unable to persist the order "on the backend"? How do I split a list into equally-sized chunks? Sorting a 10000 items list 100 times improves speed 140 times (265 ms for the whole batch instead of 37 seconds) on my rev2023.3.3.43278. Whats the grammar of "For those whose stories they are"? #kkjavatutorials #JavaAbout this Video:Hello Friends,In this video,we will talk and learn about How to Write a Java program for Sort Map based on Values (Cus. Styling contours by colour and by line thickness in QGIS. Sometimes we have to sort a list in Java before processing its elements. Each factory has an item of its own and a list of other items from competitors. All rights reserved. We can use the following methods to sort the list: Java Stream interface provides two methods for sorting the list: Stream interface provides a sorted() method to sort a list. You can create a pandas Series, using the primary list as data and the other list as index, and then just sort by the index: This is helpful when needing to order a smaller list to values in larger. Try this. You can implement a custom Comparator to sort a list by multiple attributes. unit tests. But it should be: The list is ordered regarding the first element of the pairs, and the comprehension extracts the 'second' element of the pairs.